The Simulation of Droplet Impact on the Super-Hydrophobic Surface with Micro-Pillar Arrays Fabricated by Laser Irradiation and Silanization Processes

레이저 조사 및 silanization 공정으로 제작된 micro-pillar arrays를 사용하여 초 소수성 표면에 대한 액적 영향 시뮬레이션

ZhenyanXiaa YangZhaoa ZhenYangabc ChengjuanYangab LinanLia ShibinWanga MengWangab
aSchool of Mechanical Engineering, Tianjin University, Tianjin, 300054, China
bKey Laboratory of Mechanism Theory and Equipment Design of Ministry of Education, Tianjin, 300072, Chinac
School of Engineering, University of Warwick, Coventry, CV4 7AL, UK

Received 23 September 2020, Revised 17 November 2020, Accepted 26 November 2020, Available online 11 December 2020.

Abstract

Super-hydrophobicity is one of the significant natural phenomena, which has inspired researchers to fabricate artificial smart materials using advanced manufacturing techniques. In this study, a super-hydrophobic aluminum surface was prepared by nanosecond laser texturing and FAS modification in sequence. The surface wettability turned from original hydrophilicity to super-hydrophilicity immediately after laser treatment. Then it changed to super-hydrophobicity showing a WCA of 157.6 ± 1.2° with a SA of 1.7 ± 0.7° when the laser-induced rough surface being coated with a layer of FAS molecules. The transforming mechanism was further explored from physical and chemical aspects based on the analyses of surface morphology and surface chemistry. Besides, the motion process of droplet impacting super-hydrophobic surface was systematically analyzed via the optimization of simulation calculation grid and the simulation method of volume of fluid (VOF). Based on this simulation method, the morphological changes, the inside pressure distribution and velocity of the droplet were further investigated. And the motion mechanism of the droplet on super-hydrophobic surface was clearly revealed in this paper. The simulation results and the images captured by high-speed camera were highly consistent, which indicated that the computational fluid dynamics (CFD) is an effective method to predict the droplet motion on super- hydrophobic surfaces. This paper can provide an explicit guidance for the selection of suitable methods for functional surfaces with different requirements in the industry.

Korea Abstract

초 소수성은 연구원들이 첨단 제조 기술을 사용하여 인공 스마트 재료를 제작하도록 영감을 준 중요한 자연 현상 중 하나 입니다. 이 연구에서 초 소수성 알루미늄 표면은 나노초 레이저 텍스처링과 FAS 수정에 의해 순서대로 준비되었습니다.

레이저 처리 직후 표면 습윤성은 원래의 친수성에서 초 친수성으로 바뀌 었습니다. 그런 다음 레이저 유도 거친 표면을 FAS 분자 층으로 코팅했을 때 WCA가 157.6 ± 1.2 °이고 SA가 1.7 ± 0.7 ° 인 초 소수성으로 변경되었습니다.

변형 메커니즘은 표면 형태 및 표면 화학 분석을 기반으로 물리적 및 화학적 측면에서 추가로 탐구 되었습니다. 또한, 초 소수성 표면에 영향을 미치는 물방울의 운동 과정은 시뮬레이션 계산 그리드의 최적화와 유체 부피 (VOF) 시뮬레이션 방법을 통해 체계적으로 분석되었습니다.

이 시뮬레이션 방법을 바탕으로 형태학적 변화, 내부 압력 분포 및 액 적의 속도를 추가로 조사했습니다. 그리고 초 소수성 표면에 있는 물방울의 운동 메커니즘이 이 논문에서 분명하게 드러났습니다.

시뮬레이션 결과와 고속 카메라로 캡처한 이미지는 매우 일관적 이었습니다. 이는 전산 유체 역학 (CFD)이 초 소수성 표면에서 액적 움직임을 예측하는 효과적인 방법임을 나타냅니다.

이 백서는 업계의 다양한 요구 사항을 가진 기능 표면에 적합한 방법을 선택하기 위한 명시적인 지침을 제공 할 수 있습니다.

Keywords: Laser irradiation; Wettability; Droplet impact; Simulation; VOF

Introduction

서식지에 적응하기 위해 많은 자연 식물과 동물에서 특별한 습윤 표면이 진화되었습니다 [1-3]. 연잎은 먼지에 의한 오염으로부터 스스로를 보호하기 위해 우수한 자가 청소 특성을 나타냅니다 [4]. 사막 딱정벌레는 공기에서 물을 수확할 수 있는 기능적 표면 때문에 건조한 사막에서 생존 할 수 있습니다 [5].

자연 세계에서 영감을 받아 고체 기질의 표면 습윤성을 수정하는데 더 많은 관심이 집중되었습니다 [6-7]. 기능성 표면의 우수한 성능은 고유 한 표면 습윤성에 기인하며, 이는 고체 표면에서 액체의 확산 능력을 반영하는 중요한 특성 중 하나입니다 [8].

일반적으로 물 접촉각 (WCA) 값에 따라 90 °는 친수성과 소수성의 경계로 간주됩니다. WCA가 90 ° 이상인 소수성 표면, WCA가 90 ° 미만인 친수성 표면 [9 ]. 특히 고체 표면은 WCA가 10 ° 미만의 슬라이딩 각도 (SA)에서 150 °를 초과 할 때 특별한 초 소수성을 나타냅니다 [10-11].

<내용 중략> ……

 The Simulation of Droplet Impact on the Super-Hydrophobic Surface with Micro-Pillar Arrays Fabricated by Laser Irradiation and Silanization Processes
The Simulation of Droplet Impact on the Super-Hydrophobic Surface with Micro-Pillar Arrays Fabricated by Laser Irradiation and Silanization Processes

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